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Multiple Threshold Percolation in Polymer/Filler Composites
Author(s) -
McQueen Douglas H.,
Jäger KarlMichael,
Paligová Michaela
Publication year - 2005
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.200550322
Subject(s) - percolation threshold , materials science , composite material , percolation (cognitive psychology) , percolation theory , shrinkage , crystallinity , carbon black , conductivity , polymer , particle (ecology) , electrical resistivity and conductivity , natural rubber , chemistry , oceanography , neuroscience , geology , electrical engineering , biology , engineering
Local variations in filler particle concentration and/or shape and orientation in static filler/polymer composites are modelled as distributions of percolation thresholds. The concentration variations can be due to insufficient mixing, formation of semicrystalline voids during cooling from the melt, shrinkage during polymer curing, flow during physical compression or the like. Irregular filler shapes, especially elongated shapes, reduce the percolation threshold; thus natural variations in the shapes and orientations of filler particle aggregates lead to locally varying percolation thresholds. A distribution of percolation thresholds leads to an apparent percolation threshold based on the conductivity below the mean percolation threshold. For filler concentrations above the apparent percolation threshold the dielectric constant continues to increase before reaching a lowered peak value at the mean percolation threshold and then decreasing. Own experimental results on EBA /carbon black composites support the theory.